The specific aims of this project are: 1. To procure new potentially valuable neurological, immunological and endocrinological mutants of mice that occur spontaneously in the breeding colonies of the Jackson Laboratory; 2. To characterize the new mutations genetically with respect to mode of inheritance, allelism, and linkage relationship; 3. To characterize the new mutants phenotypically with respect to fertility, longevity, growth, viability, and behavior; 4. To study the anatomical, histopathological, and physiological abnormalities of selected new mutants; 5. To develop suitable strains for maintaining and studying new and established mouse mutations so as to keep the mutant and normal allele segregating on a uniform genetic background; 6. To preserve established mutants as frozen embryos to assure their continued availability; 7. To make mutants and mutant-bearing mice available to the scientific community.